Image sensing apparatus and control method thereof

ABSTRACT

An image sensing apparatus, having an image sensor for sensing an image of an object and an analog-digital converter which operates at a predetermined frequency and converts an analog signal read from the image sensor to a digital signal, controls the relationship between a phase of the analog signal read from the image sensor and a phase of a timing signal for operating the analog-digital converter in accordance with the peripheral condition.

FIELD OF THE INVENTION

The present invention relates to an image sensing apparatus for sensingan image of an object, and a control method thereof.

BACKGROUND OF THE INVENTION

The advancement of digital image sensing apparatus such as a digitalvideo camera has been very rapid these days. The number of pixels anddensity of pixels have been improved, and a digital image sensingapparatus capable of sensing an image with the quality substantiallyequivalent to the quality of an image sensed by a conventional imagesensing apparatus using a silver halide film. In such digital imagesensing apparatus in general, analog signals obtained by photoelectricalconversion are read out from an area sensor pixel by pixel and undergoanalog-digital (A/D) conversion to form an image using the digital data.As the number of the pixels increases, the resolution of an image aswell as the quality of the image improve. However, if the processingspeed of A/D conversion does not improve, the time taken to read a frameof an image is prolonged, which makes the frame rate—the number ofimages that can be sensed per second—decrease. Accordingly, there aredesires to achieve the following: increase a reading speed of an areasensor and an A/D conversion speed, and improve a multi-channel readingtechnique of reading a frame image via a plurality of channels.

In a method of increasing the reading speed and AID conversion speed,there are problems in the response speed of an amplifier used forreading, as well as clock noise. These problems constrict a good phaserange for an A/D conversion period with respect to a read-out period.The same problems also cause phase shift, and make noise conspicuous inan image, and/or cause pattern noise. Accordingly, it was very difficultto achieve an image of high quality. As for multi-channel reading, noisegenerated in multiplexing signals read via a plurality of channels andcross-stroke between channels also constrict a good phase range for anA/D conversion period with respect to a read-out period, which alsomakes it difficult to achieve an image of high quality. In addition,pulses used for reading pixel signals from an area sensor are generatedby a timing generator (TG), and a delay since the pulses are generateduntil the signals are actually read out changes depending upontemperature. The delay also differs from one image sensor from another.Thus, it was very difficult to compensate a phase shift using a circuitso as to always perform A/D conversion with a good phase to output readsignals.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the abovesituation, and has as its object to perform A/D conversion on an outputsignal from an area sensor with a good phase in accordance with externalconditions in high-speed read-out operation.

According to the present invention, the foregoing object is attained byproviding an image sensing apparatus having an image sensor for sensingan image of an object, comprising:

an analog-digital converter that operates at a predetermined frequencyand converts an analog signal read from the image sensor to a digitalsignal; and

a controller that controls a relationship between a phase of the analogsignal read from the image sensor and a phase of a timing signal foroperating the analog-digital converter in accordance with a peripheralcondition of the image sensing apparatus.

According to the present invention, the foregoing object is alsoattained by providing an image sensing apparatus having an image sensorfor sensing an image of an object, comprising:

an analog-digital converter that operates at a predetermined frequencyand converts an analog signal read from the image sensor to a digitalsignal; and

a controller that controls a relationship between a phase of the analogsignal read from the image sensor and a phase of a timing signal foroperating said analog-digital converter on the basis of a comparisonbetween signals obtained by relatively shifting the phase of the analogsignal and the phase of the timing signal, and converting the analogsignal by said analog-digital converter for each phase.

According to the present invention, the foregoing object is alsoattained by providing a control method of an image sensing apparatushaving an image sensor for sensing an image of an object and ananalog-digital converter which operates at a predetermined frequency andconverts an analog signal read from the image sensor to a digitalsignal, comprising:

obtaining a peripheral condition of the image sensing apparatus; and

adjusting a relationship between a phase of the analog signal read fromthe image sensor and a phase of a timing signal for operating theanalog-digital converter in accordance with the peripheral condition.

According to the present invention, the foregoing object is alsoattained by providing a control method of an image sensing apparatushaving an image sensor for sensing an image of an object and ananalog-digital converter which operates at a predetermined frequency andconverts an analog signal read from the image sensor to a digitalsignal, comprising:

relatively shifting a phase of the analog signal read from the imagesensor and a phase of a timing signal for operating the analog-digitalconverter; and

determining a relationship between the phase of the analog signal readfrom the image sensor and the phase of the timing signal on the basis ofa comparison between signals obtained by converting the analog signal bythe analog-digital converter for each phase.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a block diagram illustrating a partial configuration of animage sensing apparatus according to an embodiment of the presentinvention;

FIG. 2 is a block diagram illustrating a partial configuration of theimage sensing apparatus according to the embodiment of the presentinvention;

FIG. 3 is a flowchart showing an operation of the image sensingapparatus according to the embodiment of the present invention;

FIG. 4 is a timing chart of read-out timing of an area sensor, read-outsignals, and a timing signal provided to an A/D converter;

FIG. 5 shows a timing chart showing a change of a read-out signal fromthe area sensor with respect to temperature;

FIG. 6 is a graph showing shift amounts of delay when reading signals indifferent area sensors with respect to temperature;

FIG. 7 is a diagram showing phases of a signal for operating the A/Dconverter;

FIG. 8 is a graph showing phases of the timing signal for operating theA/D converter to be used at different temperatures;

FIG. 9 is a flowchart showing processing for determining the phase ofthe timing signal for operating the A/D converter at a referencetemperature according to a first embodiment of the present invention;and

FIG. 10 is a flowchart showing processing for automatically determiningthe phase of the timing signal for operating the A/D converter in readout operation according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described indetail in accordance with the accompanying drawings.

First Embodiment

A first embodiment of the present invention will be described first.

FIGS. 1 and 2 show block diagrams of a configuration of an image sensingapparatus according to the first embodiment of the present invention.

Referring to FIG. 1, a first microcomputer 100 controls an operation ofan entire image sensing apparatus using a predetermined firmware.

EEPROM 100b can store image sensing information.

An A/D converter 100c converts analog signals from a focus detectioncircuit 105, photometry circuit 106, and a thermometer circuit 109 intodigital signals, and the first microcomputer 100 applies signalprocesses to the converted digital signals and sets correspondingstates.

The focus detection circuit 105, the photometry circuit 106, a shuttercontroller 107, a motor controller 108, a switch sensor 110, an LCDdriving circuit 111, and the thermometer circuit 109 are connected tothe first microcomputer 100. The first microcomputer 100transmits/receives signals to/from the image sensing lens 11 via mountconnection points 10. Further, the first microcomputer 100 alsotransmits/receives signals to/from an image sensing circuit block 12.The image sensing circuit block 12 will be described later withreference to FIG. 2.

Line sensors 29 are used for detecting focus states at a plurality ofpoints within an image sensing frame, and pairs of focus detectionpoints are arranged on a secondary imaging plane of an image sensingoptical system. The focus detection circuit 105 controls chargeaccumulation and reading operation of the line sensors 29 in accordancewith a signal from the first microcomputer 100, and outputs pixelinformation obtained by photoelectric conversion in the respective linesensors 29 to the first microcomputer 100.

The first microcomputer 100 performs analog-digital conversion on theinformation and performs focus detection using a known phase differencedetection method. The first microcomputer 100 exchanges signals with alens microcomputer 112 and controls focus by driving a lens based on thefocus detection information.

The photometry circuit 106 outputs signals from a multi-divisionalsensor 7 whose image sensing area is divided into a plurality of regionsto the first microcomputer 100 as luminance signals of the respectiveregions of the image sensing area.

The first microcomputer 100 performs analog-digital conversion on theluminance signals, and calculates an aperture value and shutter speedfor exposure control for image sensing operation using the convertedluminance signals.

The shutter controller 107 runs the front curtain (MG-1) and the rearcurtain (MG-2) in accordance with a signal from the first microcomputer100, thereby properly exposing an area sensor.

The motor controller 108 controls a motor in accordance with a signalfrom the first microcomputer 100, thereby moving a main mirror up anddown, and mechanically charging a shutter.

SW1 is turned on by a first stroke (e.g., a half stroke) of a releasebutton (not shown) and initiates photometry and autofocus operations.SW2 is turned on by a second stroke (e.g., a full stroke) of the releasebutton and initiates an exposure operation.

Signals from SW1, SW2 and other not-shown operating members of the imagesensing apparatus are detected by the switch sensor 110 and sent to thefirst microcomputer 100.

The LCD driving circuit 111 controls display of an LCD 41 providedwithin a finder and an LCD 42 for monitoring in accordance with signalsfrom the first microcomputer 100.

Next, a configuration of the image sensing lens 11 is explained. Theimage sensing apparatus main body and the image sensing lens 11 areelectrically connected with each other via the lens mount connectionpoints 10. The lens mount connection points 10 includes a point LO whichis a power supply connection point for a focus driving motor 16 and anaperture driving motor 17 within the image sensing lens 11, a point L1which is a power supply connection point for the lens microcomputer 112,a point L2 for a clock used for performing known serial datacommunication, a point L3 for data transmission from the image sensingapparatus to the image sensing lens 11, a point L4 for data transmissionfrom the image sensing lens 11 to the image sensing apparatus, a pointL5 which is a ground connection point of the power supply for themotors, and a point L6 which is a ground connection point of powersupply for the lens microcomputer 112.

The lens microcomputer 112 is connected with the first microcomputer 100via these lens mount connection points 10, and operates the focusdriving motor 16 and the aperture driving motor 17, thereby controllingfocus and aperture of the image sensing lens 11. Reference numerals 35and 36 denote a photodetector and a pulse plate, and the lensmicrocomputer 112 counts the number of pulses, thereby obtainingposition information of a first lens group for changing focal points,and thus focus control of the lens 11 can be performed.

Next, the image sensing circuit block 12 will be explained in detailwith reference to FIG. 2.

Reference numeral 200 denotes a second microcomputer for controlling theimage sensing circuit block 12. By transmitting/receiving signalsto/from the camera control circuit block 13 explained with reference toFIG. 1, the second microcomputer 200 controls a series of operations,such as reading pixel output from an area sensor 202 which senses animage of an object, performing A/D conversion by an A/D converter 209,forming an image, and recording the image on a recording medium 220.Reference numeral 201 denotes a timing generator (TG) and controlscharge accumulation in the area sensor 202, reading of pixel output, andoperations of a multiplexer 208 and the A/D converter 209 in accordancewith instructions from the second microcomputer 200.

Reference numeral 202 denotes the area sensor, and charges accumulatedin millions of pixels by photoelectric conversion can be read out.Reference numeral 203 denotes capacitors for temporarily storing pixeloutput of one line when reading the charges from the pixels. The chargesin every other line are read out via two channels. Reference numeral 204denotes horizontal optical black (OB) pixels which are shielded fromlight. The charges accumulated in the horizontal OB pixels 204 are alsoread out via the capacitors 203 similarly to the charges from the pixelsother than the OB pixels. Reference numeral 205 denotes vertical OBpixels which carry the same role as the horizontal OB pixels; 206,horizontal shift register which sequentially selects the pixel output ofone line temporarily stored in the capacitors 203 via two channels; 207,amplifiers for two channels which buffer pixel outputs from thecapacitors 203; and 208, the multiplexer which alternately selectsoutputs from the two channels.

The horizontal shift register 206 controls the output timing of signalsfrom the two channels so that the phases of the output signals differsby 180 degrees from each other, thus the output from the multiplexer 208has a half of the operation period of the horizontal shift register 206.Reference numeral 209 denotes an A/D converter which performs A/Dconversion sequentially on the output from the multiplexer 208 at timingin accordance with an ADTRG signal from the TG 201.

Reference numeral 210 denotes an image processing/memory control circuitwhich sequentially stores the A/D converted output from the A/Dconverter in a memory 211. Then the signal processing/memory controlcircuit 211 processes the digital data stored in the memory 211 therebyforming an image, and stores the image data in the memory 211.

Reference numeral 212 denotes a compression/expansion circuit whichcompresses and expands image data with, inter alia, adaptive discretecosine transform (ADCT). The compression/expansion circuit 212 readsimage data stored in the memory 211 and performs compression processingor expansion processing on the read image data, then writes theprocessed image data to the memory 211.

Reference 213 denotes an interface with a recording medium such as,inter alia, a memory card and hard disk; 214, a connector for connectingwith a recording medium such as, inter area, a memory card and a harddisk; and 220, a recording medium such as a hard disk.

The recording medium 220 has a recording unit 223 such as asemi-conductor memory and a magnetic disk, an interface 222 forinterfacing with the image sensing apparatus, and a connector 221 forconnecting with the image sensing apparatus. The compressed image datais recorded on the recording medium 220 via the interface 213.

Next, an operation of the image sensing apparatus according to the firstembodiment is explained with reference to FIG. 3.

In step S101, the first microcomputer 100 monitors the switch SW1 whichturns on by the first stroke of the release button. This process isrepeated until the turn-on of the switch SWI is detected. When theswitch SW1 is turns on, the process moves to the next step.

In step S102, the first microcomputer 100 obtains peripheral temperatureby A/D-converting information from the thermometer circuit 109.

In step S103, the first microcomputer 100 obtains luminance data onobjects in a plurality of areas in a frame by A/D-converting informationfrom the photometry circuit 106. The obtained luminance data iscorrected using the temperature data obtained in step S102 to a properluminance information. The shutter speed and aperture value to be usedin exposure operation (to be described later) are calculated based onthe corrected luminance information.

In step S104, the first microcomputer 100 performs focus detectionoperation with the known phase difference detection method by operatingthe focus detection circuit 105.

There are a plurality of points where focus states are detected(referred to as “distance measurement points”), and the firstmicrocomputer 100 calculates defocused amounts at the respectivedistance measurement points. Upon calculating the defocused amounts, thedefocused amounts are corrected using the temperature data obtained instep S102 to have proper defocused amounts.

The first microcomputer 100 determines at which distance measurementpoint a main object exists using a known algorithm based on thecalculated defocused amounts of the respective distance measurementpoints, and decides the determined distance measurement point as a mainpoint.

The known algorithm includes, inter alia, a near-point priority methodof selecting the nearest of the distance measurement points and a methodof grouping the distance measurement points by defocused amounts andselecting one of the groups. However, the algorithm does not directlyrelate to the present invention, the detailed explanation of it isomitted.

The first microcomputer 100 controls the focus point of the lens bycommunicating with the image sensing lens 11 so that the selecteddistance measurement point is focused.

In step S105, the first microcomputer 100 designates the LCD drivingcircuit 111 to display the shutter speed, aperture value, and focusinformation.

In step S106, the first microcomputer 100 determines whether the switchSW2 which turns on by the second stroke of the release button is ON. Ifthe switch SW2 is OFF, the processes of steps S101 to S105 are repeated,whereas if the switch SW2 is ON, the process proceeds to step S107 whereso-called exposure operation starts.

In step S107, the first microcomputer 100 initiates the exposureoperation.

The main mirror is moved up, and the lens and the aperture arecontrolled.

In step S108, the first microcomputer 100 sends a designation to thesecond microcomputer 200, in turn, the second microcomputer 200 startscharge accumulation in the area sensor 202. Further, the firstmicrocomputer 100 controls the shutter controller 107 so that adetermined shutter speed (TV) is realized.

In step S109, the second microcomputer 200 receives the temperature dataobtained in step S102 from the first microcomputer 100, and determinesthe phase of a signal for operating the A/D converter 209. The secondmicrocomputer 200 sends an instruction to the TG 201, in turn, the TG201 outputs the ADTRG signal with the determined phase to the A/Dconverter 209.

In step S110, the pixel output from the area sensor 202 is A/D-convertedby the A/D converter 209 in accordance with the ADTRG signal from the TG201, then stored in the memory 211 under control of the imageprocessing/memory control circuit 210.

The digital data stored in the memory 211 is processed by the imageprocessing/memory control circuit 210 in step S111, compressed by thecompression/expansion circuit 212, then stored in the memory 211 again.

The compressed image data is recorded on the recording medium 220 instep S112, and the series of the image sensing operation ends.

Thereafter, the process returns to step S101.

FIG. 4 is a timing chart for explaining an operation of step S110 inFIG. 3 in relation to signals from TG 201. The TG 201 generates a masterclock MCLK, and outputs signals HS_A and HS_B for driving the horizontalshift register 206. The phases of the signals HS_A and HS_B are shiftedby 180 degrees from each other, and used to read pixel outputs of oneline of the area sensor temporarily stored in the capacitors 203 via twochannels. The read outputs are indicated by Sout_A and Sout_B in FIG. 4,respectively. The TG 201 outputs a signal MPX to the multiplexer 208.Sout_A and Sout_B are multiplexed and becomes a signal “out”. The TG 201outputs to the A/D converter 209 the ADTRG signal for operating the A/Dconverter 209, and the A/D converter 209 A/D-converts the signal “out”at timing of trailing edges of the ADTRG signal. If the phases of thesignal “out” and the ADTRG signal are not properly matched, the dynamicrange may become narrow because the output becomes small, a noisy imagemay be resulted because A/D conversion is performed where the outputsignal is noisy due to MPX clock, and a striped image may be resultedbecause the phases of Sout_A and Sout_B are slightly shifted from eachother and output levels of the two channels differs from each other.Thus, it is very important to properly match the phases of the signal“out” and the ADTRG signal.

In general terms, the signal “out” is generated by multiplexing signalsSout_x read out in accordance with clock signals HS_x generated on thebasis of the master clock MCLK, while the ADTRG signal is generatedbased on the master clock MCLK signal. Since transmission of a signal isaccompanied by a delay, change in temperature causes a change in timesince the signal MCLK is generated until the signal “out” is outputted,and a change in time since the signal MCLK is generated until the ADTRGsignal is transferred to the A/D converter 209. This causes phase shiftsof the signal “out” and the signal ADTRG. FIG. 5 conceptually shows howthe relationship between phases of the signal “out” and the ADTRG signalchanges with respect to temperature. Compared to a room temperature, thesignal “out” delays for TA_1 at high temperature, while it is faster byTA_2 at low temperature. Thus, a proper phase of ADTRG changes as thetemperature changes.

FIG. 6 shows how the phase of the signal “out” proceeds and delays withrespect to temperature. In FIG. 6, the three graphs of apparatus A,apparatus B and apparatus C are shown as examples. These graphs showthat shift amounts of phases with respect to temperature are similar,but not identical for different image sensing apparatus, although thephases themselves are different for respective apparatuses.

Here, processing for determining a phase of a signal for operating theA/D converter 209 performed in step S109 in FIG. 3 will be explained indetail. As shown in FIG. 7, the phase of the ADTRG signal can beselected from the phases 1 to 8 for the signals HS_A and HS_B. In thefirst embodiment, a phase is selected from the phases 1 to 8 inaccordance with the temperature as exemplified in FIG. 8. Morespecifically, if the phase 5 is proper at the room temperature, sincethe signal “out” proceeds as the temperature decreases, the phase of theADTRG signal should be also proceeded and the phase 4 is selected. Ifthe temperature further decreases, then the phase 3 is selected. Incontrast, if the temperature is higher than the room temperature, thephase 6 is selected.

By obtaining proper phases for different temperatures and storing therelationship between the obtained proper phases and the temperatures in,for example, a memory (not shown) in the second microcomputer 200, it ispossible to quickly generate the ADTRG signal with a proper phase onlyby detecting temperature.

It should be note that the phase at the room temperature may be thephase 5, phase 4, or phase 6 depending upon an apparatus, since theproper phase differs apparatus from apparatus.

Next an operation of adjusting the phase of a signal for operating theA/D converter 209 in each image sensing apparatus, which is typicallyperformed at a factory before image sensing apparatuses are shipped, isexplained with reference to FIG. 9.

In step S201, a parameter X is substituted by a value a. The value a isan initial value of phase indicative of the maximum of the preparedphase levels for phase adjustment of the ADTRG signal. In the exampleshown in FIG. 7, the value a is “8” corresponding to the phase 8.

Next in step S202, an area sensor of the image sensing apparatus isilluminated uniformly by a predetermined amount of light, and thegenerated charges are read out and A/D-converted at timings inaccordance with the ADTRG signal of a phase (X), and sensitivities ofthe two channels are adjusted so that a predetermined value is obtained.There are a variety of methods for adjusting the sensitivities. Forinstance, gains of the amplifiers 207 for the respective two channelsmay be adjusted, a reference voltage fed to the A/D converter 209 may beadjusted, and so on.

In step S203, the parameter X is decreased by 1.

In step S204, the area sensor 202 of the image sensing apparatus isilluminated uniformly by a predetermined amount of light, and thegenerated charges are read out and A/D-converted at timings-inaccordance with the ADTRG signal with a phase (X).

In step S205, the output of an image obtained in step S204 is evaluated,and whether the phase of the ADTRG signal is proper or not isdetermined. Judgement of whether the phase of the ADTRG signal is properor not is performed as follows. When adapting an assumption that a phasewith which the maximum output level is obtained is proper, if the outputof the image obtained in step S204 is lower than the sensitivityadjusted in step S202, then the phase used in step S202 is determinedproper.

If it is determined that the phase is OK (OK in step S205, the phase isincreased by 1 in step S206 in order to obtain the phase used in stepS202 since the parameter X was decreased by 1 in step S203. Then theincreased phase is determined as the proper phase.

Whereas, if the judgement of phase of the ADTRG signal reveals no good(NG) in step S205, whether or not the parameter X decreased more thanthe limit, and if not, the process in step S202 and the subsequentprocesses are repeated. The limit is “2” which corresponds to the phase2 in a case shown in FIG. 7 so that the parameter X can be decreased instep S203.

By repeating processes from step S202 to step S205, the parameter X isdecreased one by one and the judgement is performed from, in the exampleshown in FIG. 7, the phase 8 toward the phase 1 sequentially, it ispossible to find a proper phase of the ADTRG signal.

Further, if no proper phase of the ADTRG signal has been found when theparameter X reached the last parameter, namely, when the parameter Xbecame lower than the limit, the process is determined as NG andreturned to a preceding process in a manufacturing process of the imagesensing apparatus.

Next, another method of finding a proper phase of the ADTRG signal willbe described.

When adapting an assumption that a phase with which the sensitivities ofthe outputs from the two channels are least sensitive with respect tothe phase shift is proper, the outputs of the image from the twochannels obtained in step S204 are compared, and the least outputdifference indicates that the phase used in the preceding step S202 isproper. When the difference between the outputs from the two channelsbecome large as the phase shifts, a pattern noise, such as verticalstripes will appear.

In the above description, a configuration for adjusting the phase of asignal for operating the AID converter 209 is explained. However, thepresent invention is also applicable to a case of adjusting the phase ofthe analog signal which is read out from the area sensor 202 but has notbeen inputted to the A/D converter 209 yet.

Further, in the processing shown in FIG. 9, a proper phase of the ADTRGsignal is searched from the maximum phase level (phase 8 in FIG. 7) inthe descending order. However, the proper phase may be searched from theminimum phase level (phase 1 in FIG. 7) in the ascending order. In thatcase, the parameter X is increased by 1 in step S203, and the parameterX is decreased by 1 in step S206.

Second Embodiment

Next, a second embodiment of the present invention will be explained.

In the second embodiment, variation in a phase of a signal for operatingan A/D converter specific to each image sensing apparatus and change inphase of the signal (ADTRG signal) for operating the A/D converter dueto temperature are automatically adjusted when reading signals frompixels which are located outside of an effective image sensing region ofan area sensor.

In the second embodiment, the processes of determining a phase in stepsS102 and S109 in FIG. 3 become unnecessary, and processing shown in FIG.10 is additionally performed in step S110 of reading the area sensor.Further, the adjustment performed during the production of image sensingapparatuses explained with reference to FIG. 9 becomes unnecessary.

In step S110 in FIG. 3, the output from the pixels of the area sensor202 are A/D-converted by the A/D converter 209 in accordance with theADTRG signal from the TG 201. At this time, a vertical optical blackportion 205 is read out in advance of the effective pixel area of thearea sensor 202. The operation will be explained with reference to FIG.10, and it is assumed that the phases 1 to 8 are prepared as shown inFIG. 7.

In step S301, the parameter X is substituted by “1”

In step S302, a plurality of vertical OB pixels 205 are read out andA/D-converted in accordance with the ADTRG signal with the phase (X).

In step S303, whether the parameter X is 8 or not is checked.

If the parameter X is not 8, it is increased by 1 in step S304, and theprocesses in steps S302 and S303 are repeated. In this manner, aplurality of pixels in the vertical OB portion are read out andA/D-converted in accordance with the ADTRG signal with the phases 1 to8.

In step S305, the outputs from pixels A/D-converted in accordance withthe ADTRG signals with the phases 1 to 8 are compared with each other.

In step S306, a proper phase of the ADTRG signal is determined, and thenpixels in the effective image sensing region are read out andA/D-converted in accordance with the ADTRG signal with the determinedphase.

It should be noted that, in the above processes, the proper phase issearched from the phase 1 in the ascending order, however, it is alsopossible to search from the phase 8 in the descending order.

Further, in the method of searching a proper phase of the ADTRG signalin step S306 may be basically the same as that of step S205. Namely, thephase which gives the maximum output is determined as the proper phase,or the phase which gives the least difference between outputs from thetwo channels even when the phase is changed is determined as the properphase.

Since the search in the second embodiment is performed using the outputsof the OB pixels, it may be difficult to find a proper phase since theoutput level is low comparing to the output level obtained byilluminating the image sensor as described with reference to FIG. 9.However, the output level of the OB pixels is still not too small todetermine the proper phase.

In order to improve the precision for finding the proper phase of theADTRG signal, a circuit which increase the output level of the OB pixelsto a level higher than a predetermined level may be incorporated withinthe vertical OB pixels 205 and the capacitors 203.

According to the second embodiment as described above, the phase of theADTRG signal is automatically adjusted when reading the area sensor,thus, adjustment performed in the factory upon manufacturing the imagesensing apparatus can be omitted, and the reliability of the adjustmentof the phase of the ADTRG signal improves. Furthermore, it is possibleto realize a high quality image while keeping the speed of reading thepixels high.

The present invention is not limited to the above embodiments andvarious changes and modifications can be made within the spirit andscope of the present invention. Therefore to apprise the public of thescope of the present invention, the following claims are made.

1. An image sensing apparatus having an image sensor, which has a firstarea for sensing an image of an object and a second area which isshielded from light, for sensing an image of an object, comprising: ananalog-digital converter that operates at a predetermined frequency andconverts an analog signal read from the image sensor to a digitalsignal; and a controller that controls a relationship between a phase ofa timing signal for reading out the analog signal from the image sensorand a phase of a timing signal for operating said analog-digitalconverter on the basis of signals obtained from the second area byrelatively shifting the phase of the timing signal for reading out theanalog signal and the phase of the timing signal for operating saidanalog-digital converter, and converting the analog signal by saidanalog-digital converter for each shifted phase.
 2. The image sensingapparatus according to claim 1 further comprising: a plurality of outputunits that read signals from the image sensor; and a multiplexer thatmultiplexes the signals from said plurality of output units to a timesequential signal and outputs the time sequential signal, wherein thetime sequential signal from said multiplexer is outputted to saidanalog-digital converter.
 3. The image sensing apparatus according toclaim 1, wherein said controller adjusts the relationship between thephase of the timing signal for reading out the analog signal from theimage sensor and the phase of the timing signal for operating saidanalog-digital converter so that a digital signal obtained by convertingthe signal read from the image sensor by said analog-digital converterbecomes maximum.
 4. The image sensing apparatus according to claim 2,wherein said controller adjusts the relationship between the phase ofthe timing signal for reading out the analog signal from the imagesensor and the phase of the timing signal for operating saidanalog-digital converter so that a difference between the signals fromsaid plurality of output units becomes minimum.
 5. A control method ofan image sensing apparatus having an image sensor, which has a firstarea for sensing an image of an object and a second area which isshielded from light, for sensing an image of an object, and ananalog-digital converter which operates at a predetermined frequency andconverts an analog signal read from the image sensor to a digitalsignal, comprising: determining a relationship between a phase of atiming signal for reading out the analog signal from the image sensorand a phase of a timing signal for operating said analog-digitalconverter on the basis of signals obtained from the second area byrelatively shifting the phase of the timing signal for reading out theanalog signal and the phase of the timing signal for operating saidanalog-digital converter, and converting the analog signal by saidanalog-digital converter for each shifted phase.
 6. An image sensingapparatus having an image sensor for sensing an image of an object,comprising: a temperature sensor that measures temperature; ananalog-digital converter that operates at a predetermined frequency toconvert a first analog signal to a first digital signal and convert asecond analog signal to a second digital signal, wherein the firstanalog signal and the second analog signal are read from differentpixels in a line via different channels; and a controller that controlsa relationship between a first phase of a timing signal for reading outthe first analog signal and the second analog signal from the imagesensor and a second phase of a timing signal for operating saidanalog-digital converter in accordance with the temperature measured bythe temperature sensor, wherein the relationship is controlled so as torestrain a level difference between the first digital signal and thesecond digital signal converted by said analog-digital converter, thelevel difference being produced at a timing when the first and secondanalog signals are converted into the first and second digital signals.7. The image sensing apparatus according to claim 6, further comprisinga memory that stores a plurality of different phases for the first andsecond phases of the timing signal in correspondence with differenttemperatures in advance, wherein said controller searches the first andsecond phases of the timing signal which corresponds to the measuredtemperature.
 8. The image sensing apparatus according to claim 6 furthercomprising: a plurality of output units, corresponding to the differentchannels, that read the first and second analog signals from the imagesensor; and a multiplexer that multiplexes the first and second analogsignals from said plurality of output units into a time sequentialsignal and outputs the time sequential signal, wherein the timesequential signal from said multiplexer is outputted to saidanalog-digital converter.
 9. The image sensing apparatus according toclaim 7, wherein said controller adjusts the relationship between thefirst phase of the timing signal for reading out the first and secondanalog signals from the image sensor and the second phase of the timingsignal for operating said analog-digital converter so that the digitalsignals obtained by converting the first and second analog signals bysaid analog-digital converter becomes maximum.
 10. The image sensingapparatus according to claim 7, wherein said controller adjusts therelationship between the first phase of the timing signal for readingout the first and second analog signal from said image sensor and thesecond phase of the timing signal for operating said analog-digitalconverter so that a difference between the digital signals obtained byconverting the first and second analog signals becomes minimum.